For various lubricant and functional fluid applications, there is a need for ashless (i.e., metal-free) antiwear/extreme pressure agents that can supplant conventionally used metal-containing antiwear/extreme pressure agents such as the metal salts of dialkyl dithiophosphoric acids. For decades such metal salts, especially the widely-used zinc salts, have been regarded as among the most useful compounds for this purpose. Thus countless millions of pounds of lubricants, such as gear oils and crankcase lubricating oils for passenger cars, trucks, buses, etc., have been used. Similarly, huge quantities of functional fluids, such as transmission fluids, hydraulic fluids and the like, have utilized metal dialkyl dithiophosphate antiwear/extreme pressure agents, especially the zinc dialkyl dithiophosphates.
For several reasons, including ecological, conservational and performance reasons, a need has arisen for metal-free additives capable of serving as effective replacements for the metal dialkyl dithiophosphates.
This invention is deemed to fulfill this need in an effective, efficient and economical manner.